A solid oxide fuel cell (SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Generally, a ceramic material of yttria stabilized zirconia (YSZ) is commonly used in SOFC as electrolyte to conduct oxygen ions, while a material of Ni—YSZ cermet is used as the anode material and a material of LaMnO3 is used as the cathode material.
Current SOFCs usually are built with comparatively thinner anode layer, cathode layer and electrolyte layer for reducing the polarization losses and ohmic losses in electrodes and electrolyte. Thus, it is generally required to have a support element to be designed in the fuel cell structure. Nowadays, there are many ways to support a SOFC. One common way is simply to use the solid electrolyte as the support element in a SOFC. As the ohmic loss results from the ionic conductivity through the electrolyte, an effective way to decrease ohmic resistance is to decrease the thickness of the electrolyte layer. Thus, a SOFC with a thick electrolyte layer may result in delivering a low output power.
A SOFC can use a porous metal substrate as a support element that is under the anode layer so that the thickness of electrolyte can be reduced to increase its output power. Consequently, the support element consisting of a porous metal substrate is the thickest layer in the SOFC, and is the component that provides the mechanical support. Nevertheless, although a thick layer of support element can provide a good mechanical support, the permeability of such support element can be poor so that not only it may be difficult for hydrogen to enter the anode layer, but also a water byproduct generated from the electrochemical reaction in the anode layer may not drain out of the anode layer easily. Moreover, if the water byproduct does not drain out of the anode layer in time, the path allowing hydrogen to permeate into the anode layer can be blocked to result a great polarization voltage drop on the anode side, this polarization voltage drop is due to the generated concentration gradient of hydrogen in the support element and can further affect the performance of the SOFC.
Therefore, although the permeability of the support element in SOFCs can be improved simply by reducing the thickness of the support element, it is noted that the strength of the support element may be weakened correspondingly, and consequently the long-term operation stability of the cell structure can be adversely affected.